Lethal and nonlethal suicidal behaviors are major global public health problems. Much suicidal behavior (SB) occurs after the suicide victim committed a murder or other serious transgression. The present study tested a novel evolutionary model termed the Costly Apology Model (CAM) against the ethnographic record. The bargaining model (BRM) sees nonlethal suicidal behavior as an evolved costly signal of need in the wake of adversity. Relying on this same theoretical framework, the CAM posits that nonlethal suicidal behavior can sometimes serve as an honest signal of apology in the wake of committing a severe transgression, thereby repairing valuable social relationships...

Identifying the determinants of reproductive success in small-scale societies is critical for understanding how natural selection has shaped human evolution and behavior. The available evidence suggests that status-accruing behaviors such as hunting and prosociality are pathways to reproductive success, but social egalitarianism may diminish this pathway. Here we introduce a mixed longitudinal/cross-sectional dataset based on 45 years of research with the Batek, a population of egalitarian rain forest hunter-gatherers in Peninsular Malaysia, and use it to test the effects of four predictors of lifetime reproductive success: (i) foraging return rate, (ii) sharing proclivity, (iii) cooperative foraging tendency, and (iv) kin presence...

The endogenous opioid system has received attention and extensive research for its effects on reward, pleasure, and pain. However, relative to other neurochemicals, such as oxytocin, vasopressin and dopamine, the function of opioids in regulating human attachment, sociosexuality, and other aspects of human sociality has not received much consideration. For example, nonapeptides (oxytocin and vasopressin) have been extensively studied in animals and humans for their possible roles in mother-offspring attachment, romantic attachment, fatherhood, and social cognition...

In Fig. 2 of the aforementioned article the mean value of the "chair" condition is incorrectly displayed as 0.011 when it should be 0.008. All statistics in the text are correct, and the conclusions remain the same.

The dynamics of knowledge transmission and acquisition, or how different aspects of culture are passed from one individual to another and how they are acquired and embodied by individuals, are central to understanding cultural evolution. In small-scale societies, cultural knowledge is largely acquired early in life through observation, imitation, and other forms of social learning embedded in daily experiences. However, little is known about the pathways through which such knowledge is transmitted, especially during middle childhood and adolescence...

Humans often behave more prosocially when being observed in person and even in response to subtle eye cues, purportedly to manage their reputation. Previous research on this phenomenon has employed the "watching eyes paradigm," in which adults displayed greater prosocial behavior in the presence of images of eyes versus inanimate objects. However, the robustness of the effect of eyes on prosocial behavior has recently been called into question. Therefore, the first goal of the present study was to attempt to replicate this effect...

A central hypothesis to account for the ubiquity of rituals across cultures is their supposed anxiolytic effects: rituals being maintained because they reduce existential anxiety and uncertainty. We aimed to test the anxiolytic effects of rituals by investigating two possible underlying mechanisms for it: cognitive load and repetitive movement. In our pre-registered experiment (osf.io/rsu9x), 180 undergraduates took part in either a stress or a control condition and were subsequently assigned to either control, cognitive load, undirected movement, a combination of undirected movement and cognitive load, or a ritualistic intervention...

Relationships of physical resemblance to personality similarity and social affiliation have generated considerable discussion among behavioral science researchers. A "twin-like" experimental design (involving genetically unrelated look-alikes, U-LAs) explores associations among resemblance in appearance, the Big Five personality traits, self-esteem, and social attraction within an evolutionary framework. The Personality for Professionals Inventory (PfPI), NEO/NEO-FFI-3, Rosenberg Self-Esteem Scale, and a Social Relationship Survey were variously completed by 45 U-LA pairs, identified from the "I'm Not a Look-Alike" project, Mentorn Media, and personal referrals...

We present a theory of honor violence as a form of costly signaling. Two types of honor violence are identified: revenge and purification. Both types are amenable to a signaling analysis whereby the violent behavior is a signal that can be used by out-groups to draw inferences about the nature of the signaling group, thereby helping to solve perennial problems of social cooperation: deterrence and assurance. The analysis shows that apparently gratuitous acts of violence can be part of a system of norms that are Pareto superior to alternatives without such signals...

Male-male competition is involved in inter- and intrasexual selection, with both endocrine and psychological factors presumably contributing to reproductive success in human males. We examined relationships among men's naturally occurring testosterone, their self-perceived mate value (SPMV), self-esteem, sociosexuality, and expected likelihood of approaching attractive women versus situations leading to child involvement. We then monitored changes in these measures in male rowers (N = 38) from Cambridge, UK, following a manipulated "win" or "loss" as a result of an indoor rowing contest...

Dyadic play fighting occurs in many species, but only humans are known to engage in coalitional play fighting. Dyadic play fighting is hypothesized to build motor skills involved in actual dyadic fighting; thus, coalitional play fighting may build skills involved in actual coalitional fighting, operationalized as forager lethal raiding. If human psychology includes a motivational component that encourages engagement in this type of play, evidence of this play in forager societies is necessary to determine that it is not an artifact of agricultural or industrial conditions...

This study examines steroid production in fathers watching their children compete, extending previous research of vicarious success or failure on men's hormone levels. Salivary testosterone and cortisol levels were measured in 18 fathers watching their children play in a soccer tournament. Participants completed a survey about the game and provided demographic information. Fathers with higher pregame testosterone levels were more likely to report that referees were biased against their children's teams, and pre- to postgame testosterone elevation was predicted by watching sons compete rather than daughters as well as perceptions of unfair officiating...

Among the extra-physical aspects of team sports, the ways in which players talk to each other are among the more colorful but understudied dimensions of competition. To contribute an empirical basis for examining the nature of "trash talk," we present the results of a study of 291 varsity athletes who compete in the top division among US universities. Based on a preliminary review of trash-talk topics among student-athletes, we asked participants to indicate the frequency with which they have communicated or heard others talk about opposing players' athleticism, playing ability, physical appearance, boyfriends, girlfriends, sexual behavior, parents, and home institution during competitions...

The perceived support of supernatural agents has been historically, ethnographically, and theoretically linked with confidence in engaging in violent intergroup conflict. However, scant experimental investigations of such links have been reported to date, and the extant evidence derives largely from indirect laboratory methods of limited ecological validity. Here, we experimentally tested the hypothesis that perceived supernatural aid would heighten inclinations toward coalitional aggression using a realistic simulated coalitional combat paradigm: competitive team paintball...

Work-themed play may allow children to learn complex skills, and ethno-typical and gender-typical behaviors. Thus, play may have made important contributions to the evolution of childhood through the development of embodied capital. Using data from Aka foragers and Ngandu farmer children from the Central African Republic, we ask whether children perform ethno- and gender-typical play and work activities, and whether play prepares children for complex work. Focal follows of 50 Aka and 48 Ngandu children were conducted with the aim of recording children's participation in 12 categories of work and work-themed play...

Evolutionary models consider hunting and food sharing to be milestones that paved the way from primate to human societies. Because fossil evidence is scarce, hominoid primates serve as referential models to assess our common ancestors' capacity in terms of communal use of resources, food sharing, and other forms of cooperation. Whereas chimpanzees form male-male bonds exhibiting resource-defense polygyny with intolerance and aggression toward nonresidents, bonobos form male-female and female-female bonds resulting in relaxed relations with neighboring groups...

Producing emotional tears is a universal and uniquely human behavior. Until recently, tears have received little serious attention from scientists. Here, we summarize recent theoretical developments and research findings. The evolutionary approach offers a solid ground for the analysis of the functions of tears. This is especially the case for infant crying, which we address in the first part of this contribution. We further elaborate on the antecedents and (intra- and interpersonal) functions of emotional tears in adults...

MacDonald argues that a suite of genetic and cultural adaptations among Jews constitutes a "group evolutionary strategy." Their supposed genetic adaptations include, most notably, high intelligence, conscientiousness, and ethnocentrism. According to this thesis, several major intellectual and political movements, such as Boasian anthropology, Freudian psychoanalysis, and multiculturalism, were consciously or unconsciously designed by Jews to (a) promote collectivism and group continuity among themselves in Israel and the diaspora and (b) undermine the cohesion of gentile populations, thus increasing the competitive advantage of Jews and weakening organized gentile resistance (i...